The present invention generally relates to a drawing arrangement, and more particularly, to a drawing apparatus for drawing an optical fiber in the manufacture thereof.
The optical fiber normally has a tensile strength of several hundred kg/mm.sup.2 (breaking elongation at several%), and in the longitudinal direction of the optical fiber, it is necessary to remove portions having low strength below 70 Kg/mm.sup.2 (breaking elongation at 1%). For this purpose, it has been a conventional practice to effect screening for strength guarantee by applying a constant tension over an entire length of the optical fiber so as to break the low strength portions thereof for removal. In many cases, such screening process is generally incorporated, through in-line, in the optical fiber drawing apparatus arranged to fuse an optical fiber preform by heating for drawing the optical fiber.
In a conventional optical fiber drawing apparatus as shown in FIG. 3, it is so arranged that an optical fiber preform 1 lowered at a constant speed by a feeding device 2 has its lower end fused through heating by a heating furnace 3 so as to be drawing into an optical fiber 10, and thereafter, the optical fiber thus formed is coated with resin by a coating device 4, with subsequent curing of the resin by a curing furnace 5, and then, taken up onto a capstan 6. The optical fiber is further passed through a screening portion 7, and subsequently, wound onto a winding machine 8 as a finished optical fiber 10.
In the known optical fiber drawing apparatus as described above, however, there has been such a disadvantage that when the optical fiber is broken at its low strength portion in the screening portion 7, the portion of the optical fiber 10 continuously drawing out by the capstan 6 gets entangled with the capstan 6, thus requiring a great deal of time for restoring its normal running passage, with a consequent loss in the productivity of the optical fiber.